1. Field of Invention
This present invention generally relates to autoloading firearms, specifically to gas blocks for autoloading firearms which facilitate user adjustment to change the volume of gas that flows between the barrel and the operating system.
2. Description of the Related Art
The need to regulate the flow of gas between the barrel and operating system of a firearm has been a concern since the invention of autoloading firearms. Gas is generated during the combustion of gun powder present in the cartridges used in firearms. This gas expands violently to push the bullet out of the firearm's barrel. These expanding gases are also utilized as a means to operate the action of the host firearm. In modern firearms, the preferred method of facilitating the function of an autoloading weapon is as follows. A hole, or gas port, is placed through the barrel, generally on the top. Location of the gas port varies between operating systems and gas port size is chosen to allow a broad range of ammunition to be utilized while guaranteeing the reliable function of the host firearm. Unfortunately, due to varying lengths of barrels, ammunition variance, and other factors, it is very difficult to choose a gas port size which universally works under all conditions. A popular way of compensating for these problems is to incorporate an adjustable gas block into the operating system.
Traditionally, adjustable gas blocks have been used with autoloading rifles as a means to collect, restrict, and direct the flow of gas from the barrel into the gas operating system. By controlling the amount of gas directed into the operating system, reliable operation of the host firearm is ensured while also ensuring that recoiling parts are not actuated with undue force resulting in malfunctions or premature wear and breakage of parts.
In response to military request and an increased interest in both civilian and police markets, recent firearm designs have incorporated adjustable gas blocks designed to be used in conjunction with noise suppressors or silencers. Noise suppressors provide a means to redirect and expand the gases generated from the discharge of a firearm so that the resulting flash and sound generated by the firearm is minimized or eliminated. As a result, back pressure is generated, forcing more gas into the firearm's operating system. This extra gas, or back pressure, increases the firing rate of a weapon when operating at full auto, fouls the weapon leading to premature malfunction, can cause a variety of feeding and extraction problems, and causes premature wear on the reciprocating parts of the operating system. As a result, regulating the flow of gas into a firearm's operating system and optimizing that flow for use with and without a noise suppressor has become a primary purpose of modern adjustable gas blocks.
Prior art adjustable gas blocks can, in general, be characterized by the design disclosed in U.S. Pat. No. 2,748,662. Common in the prior art is the use of an oversized gas port located on the barrel which is in communication with the gas block and gas operating system of the host firearm. The adjustable gas block is provided with an indexing means that also turns a gas cylinder, or analogous structure. The gas cylinder has a series of openings, or ports, of differing size such that, when different ports are aligned with the port of the barrel, the flow of gas from the barrel into the operating system is thereby regulated. By rotating the gas cylinder with the provided indexing means, the user is able to select the most appropriate gas flow setting based on the ammunition being used, use of a rifle grenade or the presence of a noise suppressor.
Prior art designs typically rely on the use of tools to adjust the position of the gas cylinder, an inconvenient requirement for civilian, law enforcement and military users alike. Further, many prior art designs are subject to carbon build up between the rotating gas cylinder and the gas block housing. The carbon build up can cause the gas cylinder to become locked up, making rotation very difficult without frequent maintenance. In consideration of these and other deficiencies found in the prior art, a new manner of constructing and operating an adjustable gas block is needed.